serial port problems

Brian Somers brian at
Tue May 28 02:01:54 BST 2002


Test 4 is the IRQ test - it looks like the ports aren't responding 
with irq 4/3.

sio0 survives despite the test failure because of the 0x10 flag - I 
guess the console code depends on the port actually existing....

The only thing that crosses my mind is maybe you've changed irq 3 & 4 
in your BIOS so that they're not legacy ISA irqs and something else 
is grabbing them.

> Can anyone help with this, please? I'm about to start punching things.
> The serial ports on my desktop have stopped working with kernels less than
> a few weeks old, including 4.6-RC. A "boot -v" tells me:
> sio0: irq maps: 0xa61 0x871 0x861 0xa61
> sio0: probe failed test(s): 4
> sio0 at port 0x3f8-0x3ff irq 4 flags 0x10 on isa0
> sio0: type 16550A
> sio1: irq maps: 0xa61 0xa69 0xa61 0xa61
> sio1: probe failed test(s): 4
> sio1 failed to probe at port 0x2f8-0x2ff irq 3 on isa0
> I've been playing with the BIOS settings, assuming it was something that I'd
> done. Sometimes neither port is probed OK, sometimes the first port _seems_
> OK but doesn't want to talk sense to the modem attached to it -- echo lags
> input and often doesn't happen at all. 
> The ports are OK with a kernel from mid-February, a 3.5 kernel, and when
> tested by "PC Doctor".
> Can anyone tell me exactly what "failed test 4" means, and why failing this
> test means sio0 probes OK, but sio1 fails? I've peeked into sio.c, of course, 
> but although I've hacked on the 6850, the 8250 is a mystery to me. I feel a
> bug report coming on...
> Ian.

Brian <brian at>                          <brian.somers at>
      <>                   <brian@[uk.]>
Don't _EVER_ lose your sense of humour !          <brian@[uk.]>

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